Device for providing glass layers on the inside of a tube

Abstract

A device for providing glass layers on the inside of a tube according to the PCVD process. In this process a microwave resonator is reciprocated along a tube. The resonator, on the side facing the tube, is provided partly with a heat-insulating layer. Said layer may consist of SiO 2 , Al 2 O 3 , TiO 2 or MgO.

What is claimed is: 
     
       1. A device for providing glass layers on the inside of a tube, comprising a gas supply device which is connected to one end of the tube, a furnace for heating the tube, a resonator comprising a resonant cavity for generating a plasma in the tube, said plasma being capable of delivering thermal energy to the tube in a quantity ranging from a maximum to less than 40% of the maximum, and means to move the resonator and the tube relatively with respect to each other, a high-frequency generator which is connected to the resonant cavity, and a vacuum pump which is connected to the opposite end of the tube, characterized in that the resonator comprises a cooled body comprising a duct for receiving the tube, of which body at least the wall of the duct consists of a readily heat-conducting metal and in which the wall of the duct facing the tube comprises a heat-insulating layer over only that part within which during operation of the device less than 40% of the maximum quantity of thermal energy is delivered by the plasma in the tube. 
     
     
       2. A device as claimed in claim 1, characterized in that the heat-insulating layer consists of fibres and/or grains of one or more substances from the group consisting of SiO 2 , Al 2  O 3 , TiO 2  and MgO.